Simulated Atlantic Meridional Overturning Circulation in a warmer climate and the linkage with the North Atlantic convection using EC-Earth-HR
Bibliographic record
Abstract
This study aims to analyze the effect of increasing atmospheric CO2 concentrations on the Atlantic Meridional Overturning Circulation (AMOC) and its dependence on convection in the Labrador (LAB) and Greenland (GIN) Seas. We have used EC-Earth3-HR, the high-resolution version of the global coupled climate model EC-Earth3 in this study. EC-Earth3-HR has a resolution of about 0.25 degrees in the ocean and 40 km in the atmosphere. In contrast to the HighResMIP-protocol, EC-Earth3-HR has undergone a tuning process and a multi-centennial spin-up has been performed. The set of experiments analyzed here consists of a pre-industrial control simulation (piControl), a one percent per year increase in CO2 experiment (1pctCO2) branching from year 250 of our piControl simulation, and two experiments with fixed CO2 concentrations (400.9 ppm and 551.5 ppm) branch off from two points corresponding to global temperature anomalies of around 1°C and 2°C in the 1pctCO2 experiment. Here we have defined deep convection as the mean mixed volume in March, with deep convection equal to zero when the mixed-layer is shallower than a critical depth. Our preliminary results suggest that as the climate warms, the North Atlantic waters become warmer and fresher, promoting the weakening of the North Atlantic deep convection and a subsequent reduction in AMOC strength (up to 20% reduction). The simulated overturning circulation weakening seems to be dominated by changes in LAB deep convection with GIN convection contributing less. Circulation changes in the pre-industrial and the different CO2 concentration experiments are dominated by a strong decadal variability. Compared to the standard resolution EC-Earth3-version, the use of a high resolution leads to deeper ocean mixing in LAB and GIN. More analysis has to be done on the way to clarify to what extent increased resolution affects our results in comparison with previous studies.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".